Field Investigations and SWMM Modeling of an Undeveloped Headwaters Catchment Located in the Lower Coastal Plain Region of the Southeast USA

Abstract

The southeastern region of the United States is host to a diverse variety of geophysical regions including the Blue Ridge, Piedmont, Inland Basins and Coastal Plains. Each region shows its own distinctive set of hydrological characteristics and understanding the connections between these processes is key to developing responsible watershed management practices. This thesis presents a study performed in the undeveloped headwaters of an intermittent watershed. Containing an area of 2.9 km2 the study site, referred to as WS-AGC, is located in the Coastal Plains region of Alabama. With collaboration between Auburn University and the Alabama chapter of the Associated General Contractors of America (AGC),this work intended to perform a water budget study and to assess the feasibility of sustaining a pond at WS-AGC. To achieve this goal, two separate tasks were performed. The first was the construction, deployment, monitoring and maintenance of various field monitoring facilities and equipment. These included rain gauges, weirs, groundwater observation wells and a portable weather station. The second objective focused on the development and calibration/verification of a SWMM model with respect to various hydrological conditions.

Field monitoring studied offered a glimpse on the hydrological processes related to water motion in the watershed. Such monitoring supported the development of hypotheses on the interactions between these processes at WS-AGC. These dynamics processes included; 1) the observed effects of the forested land cover on the water table level due to evapotranspiration; 2) stream flows that were either connected or not to the groundwater; 3) variations of runoff responses over seasonal fluctuations. Also, results from SW MM simulations were generally able to represent the dynamic nature of WS-AGC with regards to mean flow and total volume runoff characteristics. However, this could only be achieved with the use of groundwater compartment in the model.